1. Field of the Invention
The present invention relates to an image processing apparatus that corrects distortion of an image formed on a sheet.
2. Description of the Related Art
Machines capable of realizing image quality similar to that of printing machines have appeared with an improvement of the capability of electro-photographic apparatuses. However, in printing of such electro-photographic apparatuses, misalignment of a printing position of image data formed on a sheet may occur and distortion of the image data printed on a sheet may occur.
To resolve, among several kinds of misalignment of a printing position, misalignment occurring to the front, rear, right, and left sides in a conveyance direction in an image forming apparatus with respect to a printing position of an image printed on the front surface of a sheet and a printing position of an image printed on the rear surface of the sheet, the following method has been discussed.
First, an intermediate transfer member or a sheet on which a pattern is printed is read by an image forming apparatus. Then, misalignment occurring at a printing position is automatically adjusted based on the read result (see Japanese Patent Application Laid-Open No. 2006-276427).
In an image forming apparatus that forms an image on one sheet by repeating a process for transferring and fixing a toner image formed on an intermediate transfer member onto the sheet a plurality of times, the sheet may be irregularly deformed due to the fixing performed the plurality of times in some cases.
Specifically, the lengths of the sides perpendicular to a sheet conveyance direction among the sides of a sheet may irregularly expand or contract. For example, when the sheet conveyance direction is assumed to be the front, the front edge of the sheet contracts more than the rear edge of the sheet, and thus the sheet is deformed in a trapezoidal shape. When the sheet is irregularly deformed at the time of fixing the previous toner image in association with the distortion of the sheet, a toner image with an irregularly deformed shape is used at the time of fixing the subsequent toner image.
A technology for performing printing by a toner image with a shape deformed based on deformation of a sheet has been discussed in Japanese Patent Application Laid-Open No. 2011-43533. However, a technology has not been discussed as to a case where contraction of the length of a side formed in a conveyance direction by a position perpendicular to the conveyance direction among the sides of an image formed on a sheet (hereinafter, referred to as trapezoidal distortion) is automatically corrected.